The projection lens applied to a projector requires high imaging quality, in generally, the frame projected by the projection lens must conform to several conditions, such as a requirement of low distortion aberration, a requirement of high resolution, a requirement of high contrast, and a requirement of high uniformity, etc. In present, the wide-angle projection lens is developed to shorten the projection distance between the projector and a screen. However, the relatively problem is the designer of the projection lens must reduce the aberration derived from the wide-angle projection lens.
So far the major methods of aberration improvement include using multiple aspheric lenses, increasing the length of the projection lens, and using more number of lenses to correct the aberration, etc. Moreover, the above improvements of projection lens have produced several patents upon the projection quality, for example, U.S. Pat. No. 8,337,024, U.S. Pat. No. 8,363,318, U.S. Pat. No. 7,488,077, and U.S. Pat. No. 7,009,765, these patents are related to the projection quality improvement of the projection lens. However, the projection lens of the above patents even though improves the projection quality, the above patents can not reduce overall volume of the projection lens, and performing the above patents has a high cost shortcoming in the mass production.
Thus, how to design a projection lens having high imaging quality, small size and low cost of manufacture has become an important issue.